URL of this page: //medlineplus.gov/ency/article/007204.htm

Soy

Humans have been eating soy beans for almost 5000 years. The soybean is high in protein. The quality of protein from soy equals that of protein from animal foods.

Function

Soy in your diet can lower cholesterol. Many research studies support this claim. The U.S. Food and Drug Administration (FDA) agrees that 25 grams per day of soy protein may reduce the risk of heart disease. Health benefits of soy products may be due to their high levels of polyunsaturated fats, fiber, minerals, vitamins, and low saturated fat content.

Isoflavones that occur naturally in soy product may play a part in preventing some hormone-related cancers. Eating a diet that has a moderate amount of soy prior to adulthood may lower the risk of breast and ovarian cancer in women. However, the intake of soy in women who are postmenopausal or already have cancer remains unclear. Whole soy in products like tofu, soy milk and edamame is preferable to processed soy such as the soy protein isolates that are found in many snack products.

Using isoflavone supplements in food or pills in prevention or treatment of cancer is not recommended. However, these supplements may ease menopause symptoms such as hot flashes.

Food Sources

Not all soy protein products contain the same amount of protein. The following list ranks the protein content of some common soy foods. Highest protein items are at the top of the list.

  • Soy protein isolate (added to many soy food products, including soy sausage patties and soybean burgers)
  • Soy flour
  • Whole soybeans
  • Tempeh
  • Tofu
  • Soy milk

To find out about protein content in a soy-based food:

  • Check the Nutrition Facts label to see the grams of protein per serving.
  • Also look at the list of ingredients. If a product contains isolated soy protein (or soy protein isolate), the protein content should be fairly high.

Note: There is a difference between soy supplements in the form of tablets or capsules and soy protein products. Most soy supplements are made of concentrated soy isoflavones. These substances may help relieve symptoms of menopause. However, there is not enough evidence to support soy isoflavones for other health purposes, such as lowering cholesterol.

Side Effects

People who are not allergic to soy do not have serious side effects from eating these foods. Mild side effects may include stomach aches, constipation, and diarrhea.

Recommendations

In adults, 25 grams per day of soy protein may reduce the risk of heart disease.

Soy foods and soy-based infant formula are often used for children with dairy allergies. No studies have shown whether isolated soy protein or isoflavone supplements are useful or safe for this group. Therefore, isolated soy products are not recommended for children at this time.

Images

References

Mackay D. Soy isoflavones and other constituents. In: Pizzorno JE, Murray MT eds. Textbook of Natural Medicine. 4th ed. St Louis, MO: Elsevier Churchill Livingstone; 2013:chap 124.

Messina M, Messina VL, Chan P. Soyfoods, hyperuricemia and gout: a review of the epidemiologic and clinical data. Asia Pac J Clin Nutr. 2011;20(3):347-358. PMID: 21859653 www.ncbi.nlm.nih.gov/pubmed/21859653.

Nowak-Wegrzyn A, Sampson HA, Sicherer SH. Food allergy and adverse reactions to foods. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 151.

Sacks FM, Lichtenstein A, Van Horn L, Harris W, Kris-Etherton P, Winston M. Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee. Circulation. 2006 Feb 21;113(7):1034-1044. PMID: 16418439 www.ncbi.nlm.nih.gov/pubmed/16418439.

Taku K, Melby MK, Kronenberg F, Kurzer MS, Messina M. Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012l;19(7):776-790. PMID: 22433977 www.ncbi.nlm.nih.gov/pubmed/22433977.

Review Date 5/7/2017

Updated by: Emily Wax, RD, The Brooklyn Hospital Center, Brooklyn, NY. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.